Invasive Tick Species From Asia Rapidly Spreading In PA: What To Know

PENNSYLVANIA — An invasive tick species from Asia is rapidly spreading in Pennsylvania, with numbers significantly increasing over the last several years, environmental officials and researchers said.

Asian longhorned ticks were confined to the eastern hemisphere until at least 2013 and were not discovered in the United States until 2017. They've very quickly become prolific in southeastern Pennsylvania and in a handful of other states, with rapid growth particularly in the past several years, according to the latest figures from the Pennsylvania Department of Environmental Protection.

Indeed, over the last five years, their numbers have gone up by about 150 percent in Pennsylvania alone, according to a WHYY report, as they have taken over the mantle of the the second most common invasive tick in the state.

They are parthenogenic

Asian longhorns are like other ticks in that they love grassy and wooded areas, and that they serve as vectors for a variety of diseases. However, they are unlike some other tick species in Pennsylvania in that they are parthenogenic, which means that females can lay viable eggs without a male.

A single female tick can lay up to 3,000 eggs, and this massive offspring is responsible for the tick being discovered in hordes on certain areas and on their victims. Wildlife officials in Pennsylvania report discovering "hundreds" of ticks on individual animals.

What diseases do they transmit?

Fortunately, it appears as though they do not transmit lyme disease, and while they're capable of transmitting diseases like Rocky Mountain spotted fever to humans and animals alike, there's not yet evidence that they've done so on a wide scale in the United States. Research is still underway on the tick's relatively new interactions with American environments, and its disease vectors and behaviors Japan, China, Korea, and Russia are not necessarily indicative of what it will do here, officials say.

Still, Asian longhorns pose a significant and immediate threat in other ways. Most notably, they carry and transmit Theileria orientalis, a disease which causes often fatal anemia and fever in cattle, the DEP says.

What to watch for

Asian longhorned ticks are chiefly active in warmer weather, from spring through fall, though Penn State Extension researchers say that nymphs seem to peak in activity in the late spring, while adults are more active in June to August.

The ticks are not large: adults are about an eighth of an inch wide, including legs, and nymphs are much smaller. They are deep copper or red in color, and have eight legs as adults.

The Asian tick is easily confused with other tick species, as its distinctive “horns” may not always be visible without a microscope.

“Even experts have difficulty distinguishing among tick species, so it is important to take precautions to protect pets, livestock and family members from becoming a host for ticks of any kind,” State Veterinarian Dr. David Wolfgang urged. “Scientists don’t yet know how this species will adapt to the North American climate and animal hosts, but we know it survived New Jersey’s winter and has infested sheep and cattle in this region.”

If you are bitten by an Asian longhorned tick or find one, store the tick in a container with rubbing alcohol, DEP recommends. Contact your county health department or doctor if the tick was on you. If it was on your pet, contact your veterinarian. If removed from livestock, contact your veterinarian in addition to the Pennsylvania Department of Agriculture.

Range

Samples of the Asian longhorned tick have been found in 17 states. They're predominantly along the eastern seaboard, though they've ranged out to the midwest. Locations include New Jersey, Pennsylvania, Delaware, New York, Ohio, West Virginia, Virginia, Kentucky, Tennessee, Maryland, North Carolina, South Carolina, Georgia, Missouri, Arkansas, Connecticut, and Massachusetts.

In Pennsylvania, they've spread as far as 27 counties, mostly in the southern half of of the state, according to the DEP. The concentration is highest in the southeastern part of the state and central New Jersey.

The range is expected to increase dramatically to cover large portions of the country, according to a Jan. 2024 report from the US Department of Agriculture.

"Several habitat suitability models suggest that populations of this tick species could potentially inhabit most of the eastern half of the United States and areas on the Pacific Coastline," USDA biologists said. "In areas outside of the United States, where it is established, the ALHT adapts to a wide range of environmental conditions, but invasive populations elsewhere prefer mild temperatures and humid climates."

Impact on cattle and wildlife

Researchers at Ohio State University concluded that a 2021 infestation of Asian longhorned ticks was behind the deaths of three cattle, including a previously healthy adult bull who died of severe blood loss from tick bites, according to a news release.

The bull was 5 years old and “enormous,” Risa Pesapane, the senior author of the paper published in the Journal of Medical Entomology and an assistant professor of preventive medicine at Ohio State, said in a news release.

“To have been taken down by exsanguination by ticks, you can imagine that was tens of thousands of ticks on one animal,” said Pesapane.

The ticks feed mainly on deer and raccoons but have also been found on dogs and cats, cattle sheep, goats, horses, squirrels, rabbits, skunks, opossums and groundhogs.

The tiny brown ticks are about the size of a sesame seed in some stages and pea size when engorged. Females reproduce asexually and can lay up to 2,000 eggs at a time. Their offspring can do the same.

“There are no other ticks in North America that do that. So they can just march on, with exponential growth, without any limitation of having to find a mate,” Pesapane said. “Where the habitat is ideal, and anecdotally it seems that unmowed pastures are an ideal location, there’s little stopping them from generating these huge numbers.”

Researchers estimated there were about 1 million longhorned ticks in the pasture of about 25 acres where the cattle that died had been grazing. A pesticide application in 2021 eradicated the ticks, but they returned a year later.

“The good news about the ticks, though, is that most tick control agents that we currently have seemed to kill them,” Pesapane said. “Still, managing them is not easy because of how numerous they are and how easily they can come back.”

Pesticide applications have limits, though. Asian longhorned ticks hide easily in vegetation, and unless the pesticide is applied directly to the insect, they’re likely to survive.
The best recourse is to target them early in the growing season when adults become active again, but before they lay eggs.

“But for a variety of reasons, I tell people you cannot spray your way out of an Asian longhorned tick infestation — it will require an integrated approach,” Pesapane said.

With reporting from Patch correspondent Michelle-Rotuno Johnson